

fn^ — %"v — frv — 



Thr tJnr- 



FIG. 23. Potentials recorded froin endocardium to epicar- 

 dium in the mid-lateral left ventricular wall of the rhesus 

 monkey. A: unipolar potentials; B: bipolar potentials. Termi- 

 nals 1, 2, and 3 of the unipolar record show characteristic 

 central left cavity records. Terminal 15, from which no unipolar 

 record was taken, was at the epicardial surface. Bipolar channel 

 I records the potential difference between unipolar records i 

 and 2, and bipolar channel 2 records the potential difference 

 between 2 and 3, etc. Channel 15 records the fixed time- 

 reference potential, and channel 16 the lead II QRS. Time 

 pips at 5 msec intervals. Downward bipolar records indicate 

 movement of the wave from inside out. [From Scher & Young 

 (ii7)-] 



60 per cent of the wail thickness. Sciier and co- 

 workers have tended to minimize the importance of 

 the reversals of direction within the wall and of the 

 endocardially directed portion of the activation wave, 

 although many examples of this phenomenon have 

 been presented in data published by this group 

 (119, 120). There is often no evidence for Purkinje 

 penetration along an electrode in the dog or monkey 

 heart (fig. 23). They have also stressed the fact that 

 activation under the papillary muscles and some 

 trabeculations originates in the middle of the wall 

 and moves toward both surfaces. Durrer & van der 

 Tweel (41) state, "In the area where most of our 

 experiments were performed, the area bounded by a 

 line I cm apical of the sulcus atrioventricularis, the 

 left side of the ventricular septum and the lateral 



EXCITATION OF THE HEART 3O3 



2-3 4-5 5-6. 6-7 



3-4 



3.4 



r 



J J 



3-4 



f » r 



\50my. 



\2mv. 



7-a 





8-9 



9-10 



3-4 



50msec 



r- 3-4 r 



FIG. 24. Bipolar potentials recorded at i mm intervals within 

 the left ventricular wall of the dog heart. First and third lines 

 show potentials recorded at various positions from inside out 

 in the wall; these 2ire compared with the potential recorded 

 at a fixed place in the wall, between terminals 3 and 4. Po- 

 tentials recorded at this point make up the second and fourth 

 line of traces. Note that the potentials are downward on 4-5, 

 upward on 5-6, downward on 6-7, and finally upward on 

 7-8, 8-9, and 9-10. This indicates that conduction was moving 

 from inside out only between 5 and 6, and between 7 and 10. 

 The small spike at the beginning of 3-4, the reference, is con- 

 sidered due to intramural Purkinje fibers. [From Durrer & 

 van der Tweel (41).] 



part of the left ventricular wall between the insertions 

 in the papillary muscles — the depth most frequently 

 found was two-fifths of the diastolic thickness of the 

 wall. In some instances only two or three of 8 terminals 

 showed successive activation." [See fig. 24.] 



Durrer and his colleagues found it more difficult 

 to estimate Purkinje penetration on the apical portion 

 of the ventricular wall. They obtained the same re- 

 sults (earliest activation within the wall rather than 

 on the endocardial surface) near the base of the heart 

 with the exception that 2 1 per cent of the places 

 examined in that region showed no Purkinje pene- 

 tration. These investigators apparently feel that 

 Purkinje penetration in the goat is similar to that 

 which they believe exists in the dog (see below). 



Sodi-Pallares states his results somewhat diflferently. 



"For purposes of didactic discussion, the muscular 

 mass comprising the free walls of the ventricles may 

 be considered to consist of an inner ^3 (sub-endo- 

 cardial) and another I3 (sub-epicardial). Propaga- 

 tion through the former is rapid, figures of i or 2 



